Back to EveryPatent.com
United States Patent |
6,115,231
|
Shirakawa
|
September 5, 2000
|
Electrostatic relay
Abstract
An electrostatic relay comprises: a torsional elasticity portion supported
on a substrate such that a gap is maintained from the substrate and
arranged to have a beam shape; a movable structure portion which can be
rotated by dint of elastic support of the torsional elasticity portion; at
least one movable contact provided for at least an end of the movable
structure portion; a movable electrode disposed between a fulcrum P of
rotation of the movable structure portion and the movable contact; at
least one fixed contact formed on the substrate at a position opposite to
the movable contact such that contact is permitted; and a fixed electrode
formed on the substrate at a position opposite to the movable electrode,
wherein at least a portion between the fulcrum P of rotation of the
movable structure portion and the movable contact is formed into an
elastic connection portion.
Inventors:
|
Shirakawa; Yukihiko (Chiba, JP)
|
Assignee:
|
TDK Corporation (Tokyo, JP)
|
Appl. No.:
|
196128 |
Filed:
|
November 20, 1998 |
Foreign Application Priority Data
| Nov 25, 1997[JP] | 9-339309 |
| Jan 12, 1998[JP] | 10-014754 |
Current U.S. Class: |
361/233; 200/181 |
Intern'l Class: |
H01H 059/00 |
Field of Search: |
361/233-235
200/181
|
References Cited
U.S. Patent Documents
4078183 | Mar., 1978 | Lewiner et al. | 200/181.
|
5629565 | May., 1997 | Schlaak et al. | 200/181.
|
5666258 | Sep., 1997 | Gevatter et al.
| |
5677823 | Oct., 1997 | Smith | 361/233.
|
Foreign Patent Documents |
2-100224 | Apr., 1990 | JP.
| |
3-112032 | May., 1991 | JP.
| |
4-58430 | Feb., 1992 | JP.
| |
405002977 | Jan., 1993 | JP.
| |
405002978 | Jan., 1993 | JP.
| |
405002975 | Jan., 1993 | JP.
| |
8-506690 | Jul., 1996 | JP.
| |
Primary Examiner: Fleming; Fritz
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Claims
What is claimed is:
1. An electrostatic relay comprising:
a substrate;
a torsional elasticity portion supported on said substrate such that a gap
is maintained from said substrate and arranged to have a beam shape;
a movable structure portion rotatably supported by said torsional
elasticity portion;
at least one movable contact provided at an end of said movable structure
portion;
a movable electrode disposed between a fulcrum of rotation of said movable
structure portion and said movable contact;
at least one fixed contact formed on said substrate at a position opposite
to said movable contact such that contact is permitted; and
a fixed electrode formed on said substrate at a position opposite to said
movable electrode;
wherein at least one portion between the fulcrum of rotation of said
movable structure portion and said movable contact is formed into an
elastic connection portion.
2. An electrostatic relay according to claim 1, wherein said elastic
connection portion is formed between said movable electrode and said
movable contact of said movable structure portion, and when voltage is
applied between said movable electrode and said fixed electrode, elastic
deformation causes said movable contact and said fixed contact to be
brought into contact with each other in a parallel state.
3. An electrostatic relay according to claim 1, wherein said elastic
connection portion is formed between said fulcrum of rotation of said
movable structure portion and said movable electrode, when voltage is
applied between said movable electrode and said fixed electrode, elastic
deformation causes said movable electrode to be sucked in parallel with
said fixed electrode or into an approach state near the parallel state.
4. An electrostatic relay according to claim 1, wherein said elastic
connection portion is portionally deformed.
5. An electrostatic relay according to claim 1, wherein said elastic
connection portion is deflectively deformed.
6. An electrostatic relay according to claim 1, wherein said movable
electrode is formed on a lower surface of the movable structure portion.
7. An electrostatic relay according to claim 6, wherein a dielectric layer
is interposed between said movable electrode and said fixed electrode.
8. An electrostatic relay according to claim 1, wherein said movable
electrode is formed on an upper surface of the movable structure portion.
9. An electrostatic relay according to claim 1, wherein said movable
structure portions extend to both sides of said torsional elasticity
portion, said movable contact is provided for at least either side with
respect to said fulcrum of rotation, said movable electrodes are provided
for both sides, and said fixed electrodes are formed on said substrate at
positions opposite to said movable electrodes.
10. An electrostatic relay comprising:
a substrate;
a torsional elasticity portion supported on said substrate such that a gap
is maintained from said substrate and arranged to have a beam shape;
a movable structure portion disposed to intersect said torsional elasticity
portion and rotatably supported by said torsional elasticity portion;
movable electrode portions rotatively provided for both sides of a fulcrum
of rotation of said movable structure portion through elastic connection
portions;
movable electrodes constituted by said movable electrode portions or
provided for said movable electrode portions;
fixed electrodes disposed on said substrate at positions opposite to said
movable electrodes;
at least one movable contact provided for at least an end of said movable
structure portion; and
a fixed contact disposed on said substrate at a position opposite to said
movable contact such that contact is permitted.
11. An electrostatic relay according to claim 10, wherein a movable end of
each of said movable electrode portions is disposed adjacent to said
fulcrum of rotation of said movable structure portion.
12. An electrostatic relay according to claim 10, wherein said elastic
connection portion has a structure with which said movable electrode is
caused to approach said fixed electrode by dint of elastic deformation
when voltage is applied between said movable electrode and said fixed
electrode.
13. An electrostatic relay according to claim 10, wherein said movable
electrode is formed on a lower surface of the movable structure portion.
14. An electrostatic relay according to claim 11, wherein a dielectric
layer is interposed between said movable electrode and said fixed
electrode.
15. An electrostatic relay according to claim 10, wherein said movable
electrode is formed on an upper surface of the movable structure portion.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic relay incorporating an
electrostatic actuator which uses electrostatic attractive force as a
drive source thereof.
An electrostatic relay is different from a conventional electromagnetic
relay which uses an electromagnet in a structure that electrostatic
attractive force is used as drive force to open/close contacts thereof.
Since any coil for generating electromagnetic force is not required, the
number of mechanical elements can be reduced. Moreover, the size reduction
can be permitted. Since the electrostatic actuator, which is intrinsically
a capacitor, is employed as the drive source, electric power consumption
can be reduced. Therefore, research and development have been performed to
put the electrostatic relay to practical use.
An electrostatic relay of the foregoing type has been disclosed in, for
example, Japanese Patent Laid-Open No. 2-100224. That is, single crystal
Si is selectively etched so that an elastic torsion bar and a seesaw
structure connected to the elastic torsion bar are formed. Moreover, a
movable electrode of the electrostatic actuator and a movable contact of
the relay are provided for the seesaw structure so as to be disposed on an
electrically insulating substrate through a spacer, the electrically
insulating substrate having a fixed electrode and a fixed contact disposed
at opposite positions.
The above-mentioned electrostatic relay has a structure that the elastic
torsion bar is twisted when voltage is applied between the fixed electrode
and the movable electrode when the electrostatic relay is operated. Thus,
the seesaw structure in the portion applied with the voltage performs a
rotational motion so that the movable contact is brought into contact with
the fixed contact.
The above-mentioned conventional electrostatic relay has the following
problem when a relay contact in the form of a pair of the movable contact
and a fixed contact is opened/closed.
When the relay contact is closed, the conventional electrostatic relay is
arranged such that voltage is applied between the movable electrode of the
electrostatic actuator provided for the seesaw structure adjacent to the
target contact and the fixed electrode adjacent to the substrate.
Electrostatic attractive force acting between the two electrodes is used
to cause the seesaw structure to perform a seesaw motion such that the
elastic torsion bar serves as a fulcrum of rotation. Thus, the movable
contact is brought into contact with the fixed contact so that the contact
is closed.
Since the foregoing electrostatic relay has the movable contact provided
for the end of the seesaw structure, the movable contact is brought into
contact with the fixed contact in a state in which the movable contact is
inclined. Therefore, a satisfactorily large contact area cannot be
realized and the contact resistance is raised excessively. If the position
of the structure which is provided with the movable contact is not
appropriately selected, the structure is undesirably brought into contact
together with the movable contact. Thus, there is a possibility that the
pressure between the contacts becomes insufficiently low.
The electrostatic relay having the above-mentioned structure is formed such
that the movable electrode opposite to the fixed electrode is formed
adjacent to the fulcrum of rotation as compared with the movable contact
of the seesaw structure held by the elastic torsion bar such that a gap is
maintained. Therefore, when the movable contact has been brought into
contact with the fixed contact and thus the rotational motion of the
seesaw structure has been interrupted, a wedge shape air gap is generated
between the fixed electrode and the movable electrode.
However, the electrostatic attractive force is in proportion to the inverse
square of the gap between the two electrodes. Therefore, the electrostatic
actuator encounters reduction in the electrostatic attractive force owning
to the great air gap even during the suction operation. Since a
sufficiently high pressure is not applied to the contact, the resistance
of the contact cannot satisfactorily be reduced. If the operating voltage
is raised to overcome the foregoing problem, the practicality of the
electrostatic relay excessively deteriorates.
If the resistance of the contact is high, the contact is overheated by dint
of Joule heat when a contact electric current is supplied. Thus, a
phenomenon that the contact is melted easily takes place. When the
operating voltage is raised to reduce the high contact resistance so as to
raise the contact pressure, the practicality of the electrostatic relay
excessively deteriorates.
When the relay contact is opened, the following problem arises.
That is, when the relay contact is opened, the movable contact and the
fixed contact must be separated from each other. In the foregoing case,
the fixed electrode and the movable electrode of the electrostatic
actuator are short-circuited to make the electrostatic attractive force
between the electrodes to be zero. As a result, restoring force of the
elastic torsion bar which rotatably supports the seesaw structure acts so
that the movable contact is moved upwards. Thus, the contact with the
fixed contact is suspended.
As described above, when the relay contact of the conventional
electrostatic relay is opened, only the restoring force of the elastic
torsion bar serving as the torsional elastic member is the separating
force. If a high contact electric current is applied and thus the contact
is melted, the force for forcibly separating the contacts from each other
is insufficiently small.
To prevent the above-mentioned fact, the restoring force of the elastic
torsion bar is required to be enlarged. In the foregoing case, also the
force for closing the relay contact is enlarged. Therefore, the voltage
which must be applied to the electrostatic relay must be raised. Thus, the
practicality of the electrostatic relay excessively deteriorates.
As a method of enlarging the force for opening the relay contact, a method
may be employed whereby voltage is applied between the fixed electrode and
the movable electrode of the electrostatic actuator (hereinafter called an
"opposite electrode") opposite to the closed contact of the seesaw
structure of the electrostatic relay so as to generate electrostatic
attractive force. Thus, the force for upward moving the seesaw structure
closing the contact is generated.
However, since the movable electrode of the electrostatic actuator of the
opposite electrode is moved upwards, the distance from the fixed electrode
is elongated.
Since the force for rotating the seesaw structure is the force of a lever,
the force is a product of a distance from the central axis of rotation and
the attractive force at the foregoing position. The distance between the
fixed electrode and the movable electrode is elongated in proportion to
the distance from the central axis of rotation. Since the electrostatic
attractive force acting at the electrodes is in proportion to the inverse
square of the distance between the electrodes, the attractive force of the
electrostatic actuator at the opposite electrode is reduced excessively.
Therefore, the foregoing attractive force cannot satisfactorily separate
the contacts from each other. Thus, if the voltage which is applied to the
opposite electrode is not raised, the force for separating the relay
contact cannot easily be enlarged.
As described above, the conventional electrostatic relay encounters
excessively high contact resistance when the contact has been closed.
Thus, the phenomenon that the contact is melted easily takes place. Since
the force for separating the contacts from each other is too small, a
failure that the contacts are melted takes place if the contacts are
melted. Therefore, a satisfactorily high contact electric current cannot
be maintained. Thus, the reliability and practicality are unsatisfactory.
To solve the above-mentioned problems, the voltage for operating the
electrostatic relay must be raised. However, the high operating voltage
excessively deteriorates the practicality of the electrostatic relay.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide
a practical electrostatic relay exhibiting low-voltage operation, low
contact resistance and a large contact capacity.
To achieve the foregoing objects, according to first aspect of the present
invention, there is provided an electrostatic relay comprising: a
substrate; a torsional elasticity portion supported on the substrate such
that a gap is maintained from the substrate and arranged to have a beam
shape; a movable structure portion which can be rotated by dint of elastic
support of the torsional elasticity portion; at least one movable contact
provided for at least an end of the movable structure portion; a movable
electrode disposed between a fulcrum of rotation of the movable structure
portion and the movable contact; at least one fixed contact formed on the
substrate at a position opposite to the movable contact such that contact
is permitted; and a fixed electrode formed on the substrate at a position
opposite to the movable electrode, wherein at least a portion between the
fulcrum of rotation of the movable structure portion and the movable
contact is formed into an elastic connection portion.
It is preferable that the electrostatic relay has a structure that the
elastic connection portion is formed between the movable electrode and the
movable contact of the movable structure portion, and when voltage is
applied between the movable electrode and the fixed electrode, elastic
deformation causes the movable contact and the fixed contact to be brought
into contact with each other in a parallel state.
It is preferable that the elastic connection portion is formed between the
fulcrum of rotation of the movable structure portion and the movable
electrode, when voltage is applied between the movable electrode and the
fixed electrode, elastic deformation causes the movable electrode to be
sucked in parallel with the fixed electrode or into an approach state near
the parallel state.
A dielectric layer may be interposed between the movable electrode and the
fixed electrode.
A structure may be employed in which the movable structure portion extends
to two sides of the torsional elasticity portion in the form of the beam
shape, the movable contact is provided for at least either side with
respect to the fulcrum of rotation, the movable electrodes are provided
for both sides, and the fixed electrodes are formed on the substrate at
positions opposite to the movable electrodes. To achieve the foregoing
objects, according to second aspect of the present invention, there is
provided an electrostatic relay comprising: a substrate; a torsional
elasticity portion supported on the substrate such that a gap is
maintained from the substrate and arranged to have a beam shape; a movable
structure portion disposed to intersect the torsional elasticity portion
and elastically supported by the torsional elasticity portion so that
rotation is permitted; movable electrode portions ratably provided for
both sides of a fulcrum of rotation of the movable structure portion
through elastic connection portions; movable electrodes constituted by the
movable electrode portions or provided for the movable electrode portions;
fixed electrodes disposed on the substrate at positions opposite to the
movable electrodes; at least one movable contact provided for at least an
end of the movable structure portion; and a fixed contact disposed on the
substrate at a position opposite to the movable contact such that contact
is permitted.
It is preferable that the foregoing electrostatic relay has a structure
that a movable end of each of the movable electrode portions is disposed
adjacent to the fulcrum of rotation of the movable structure portion.
It is preferable that the elastic connection portion has a structure with
which the movable electrode is caused to approach the fixed electrode by
dint of elastic deformation when voltage is applied between the movable
electrode and the fixed electrode.
Another structure may be employed in which a dielectric layer is interposed
between the movable electrode and the fixed electrode.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view showing a first embodiment of an electrostatic relay
according to the present invention;
FIG. 2 is a side cross sectional view taken along line II--II shown in FIG.
1;
FIG. 3 is a side cross sectional view showing an intermediate state in
which the contacts according to the first embodiment are being turned on;
FIG. 4 is a side cross sectional view showing a state in which the
operation for turning the contacts according to the first embodiment on
has been completed;
FIG. 5 is a plan view showing a second embodiment of the present invention;
FIG. 6 is a side cross sectional view taken along line VI--VI shown in FIG.
5;
FIG. 7 is a side cross sectional view showing an intermediate state of an
operation for turning the contacts on in the second embodiment;
FIG. 8 is a side cross sectional view showing a state in which the
operation for turning the contacts on in the second embodiment has been
completed;
FIG. 9 is a plan view showing a third embodiment of the present invention;
FIG. 10 is a side cross sectional view taken along line X--X shown in FIG.
9;
FIG. 11 is a side cross sectional view showing a state in which the
operation for turning the contacts on has been completed in the third
embodiment;
FIG. 12 is a plan view showing a fourth embodiment of the present
invention;
FIG. 13 is a cross sectional view taken along line XIII--XIII shown in FIG.
12;
FIG. 14 is a waveform graph showing waveform of voltage which is applied
between electrodes of a pair of electrostatic actuators according to the
fourth embodiment;
FIG. 15 is a circuit diagramshowing a structure in which a switch is formed
in the fourth embodiment;
FIG. 16 is a plan view showing the embodiment of the present invention;
FIG. 17 is a cross sectional view taken along line XVII--XVII shown in FIG.
16;
FIGS. 18A to 18C are diagrams showing a process for manufacturing the
electrostatic relay according to the embodiment of the present invention;
FIG. 19 is a plan view showing a fifth embodiment of an electrostatic relay
according to the present invention;
FIG. 20 is a front cross sectional view taken along line II--II shown in
FIG. 19;
FIG. 21 is a front cross sectional view showing an intermediate state in
which the contacts according to the fifth embodiment is being turned on;
FIG. 22 is a front cross sectional view showing a state in which the
operation for turning the contacts according to the fifth embodiment on
has been completed;
FIG. 23 is a front cross sectional view showing a state in which the
voltage applied to the electrostatic relay has been made to be zero after
the contacts have been turned on in the structure according to the fifth
embodiment;
FIG. 24 is a front cross sectional view showing an intermediate state
according to the fifth embodiment in which the contacts are being turned
off;
FIG. 25 is a front cross sectional view showing a state according to the
fifth embodiment in which the operation for turning the contacts off has
been completed;
FIG. 26 is a plan view showing a sixth embodiment of the electrostatic
relay according to the present invention;
FIG. 27 is a front cross sectional view taken along line IX--IX shown in
FIG. 26;
FIG. 28 is a front cross sectional view showing an intermediate state of
the operation for turning the contacts on in the sixth embodiment of the
present invention;
FIG. 29 is a front cross sectional view showing a state in which the
operation for turning the contacts on has been completed in the sixth
embodiment;
FIG. 30 is a front cross sectional view showing a state in which the
voltage applied to the electrostatic actuator has been made to be zero
after the contacts have been turned on in the sixth embodiment;
FIG. 31 is a front cross sectional view showing an intermediate state of
the operation for turning the contacts off in the sixth embodiment;
FIG. 32 is a front cross sectional view showing a state in which the
operation for turning the contacts off has been completed in the sixth
embodiment;
FIG. 33 is a plan view showing the embodiment of the present invention;
FIG. 34 is a front cross sectional view taken along line XVI--XVI shown in
FIG. 33; and
FIGS. 35A to 35C are diagrams showing a process for manufacturing the
electrostatic relay according to the embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of an electrostatic relay according to first aspect of the
present invention will now be described with reference to the drawings.
First Embodiment
FIGS. 1 to 4 show a first embodiment of an electrostatic relay according to
the present invention. Referring to the drawings, the electrostatic relay
incorporates an insulating substrate 1, an anchor structure 2 stood erect
on the substrate 1 and secured to the same, an elastic torsional portion 3
held such that a gap is maintained from the substrate 1 and formed into a
beam shape and a movable structure portion 10 formed into a relay
structure which is able to rotate by dint of elastic support performed by
the elastic torsional portion 3. The insulating substrate 1 has a
structure that at least the surface thereof is subjected to an insulating
process. For example, the substrate 1 is a single crystal Si substrate
having a SiO2 insulating layer formed on the surface thereof. The three
elements, which are the anchor structure 2, the elastic torsional portion
3 in the form of the beam shape and the movable structure portion 10, are
integrally formed by polycrystal Si or the like.
The movable structure portion 10 constituting the relay structure
incorporates a beam connection portion 11 connected to the elastic
torsional portion 3, a movable-electrode support portion 12, a
movable-contact support portion 13 and an elastic connection portion 14
for connecting the movable-electrode support portion 12 and the
movable-contact support portion 13 to each other. The elastic connection
portion 14 is formed into the beam shape. When the elastic connection
portion 14 is twisted, the movable-contact support portion 13 can be
rotated.
The movable structure portion 10 which is the relay structure has, on the
surface opposite to the substrate, a movable electrode 20, an insulating
layer (a dielectric layer) 21 covering the surface of the movable
electrode 20 and a movable contact 22, as shown in FIGS. 2 to 4. A fixed
electrode 4 and a fixed contact 5 are formed on the surface of the
substrate opposite to the foregoing surface of the movable structure
portion 10. The fixed electrode 4 secured to the surface of the insulating
substrate 1 and the movable electrode 20 secured to the movable-electrode
support portion 12 constitute an electrostatic actuator which generates
electrostatic attractive force when voltage is applied between the
electrodes. The fixed electrode 4 and the movable electrode 20 are
connected to an outer power source through electric wires (not shown).
The principle of the operation of the electrostatic relay according to the
first embodiment will now be described. FIG. 2 shows the positions of the
electrodes and the contacts in a non-operation state (in a state where no
voltage is applied). In the foregoing state, the portion between the
contacts 5 and 22 is opened. When voltage is applied between the fixed
electrode 4 and the movable electrode 20 constituting the electrostatic
actuator, electrostatic attractive force is generated between the two
electrodes. As shown in FIG. 3, the movable structure portion 10 which is
the relay structure is rotated toward the substrate by dint of the
torsional elasticity of the elastic torsional portion 3 in the form of the
beam shape until the movable contact 22 is brought into contact with the
fixed contact 5. The fulcrum of rotation is the position of line P shown
in FIG. 1.
The operation of the relay structure of the conventional electrostatic
relay was interrupted in this state. At this time, the movable contact 22
and the fixed contact 5 are in a state of point contact as can be
understood from FIG. 3. Therefore, a satisfactorily large contact area
cannot be obtained and the contact resistance is raised excessively. Since
the contact point is too small to reduce the resistance, electric currents
are concentrated. Thus, the temperature of the contact is raised and
therefore a failure of a type that the contact is melted easily takes
place. Since the distance from the fixed electrode 4 to the movable
electrode 20 of the electrostatic actuator is too long, satisfactorily
large electrostatic attractive force cannot be generated. Therefore, a
satisfactorily contact pressure cannot be realized. It leads to a fact
that the contact resistance is raised. To raise the contact pressure,
higher voltage must be applied. In this case, the operating voltage for
the electrostatic relay is raised excessively to realize practicality.
However, the electrostatic relay according to this embodiment has a
structure that the elastic connection portion 14 is deformed by dint of
the sucking force of the electrostatic actuator. Thus, the elastic
connection portion 14 is deformed such that the movable contact 22 is
brought to be parallel to the fixed contact 5, as shown in FIG. 4. As can
be understood from FIG. 4, the contacts 5 and 22 are in plane contact with
each other such that the contacts 5 and 22 are in parallel with each
other. Thus, a pair of the fixed contact 5 is short-circuited by the
movable contact 22 so that sufficiently low contact resistance and a
satisfactorily large contact electric current capacity can be realized.
Moreover, the distance between the electrodes 4 and 20 of the
electrostatic actuator can considerably be shortened as compared with the
state shown in FIG. 3. Since the electrostatic attractive force is in
inverse proportion to the square of the distance between the electrodes, a
sufficiently high pressure can be applied to the contacts even if the
operating voltage is low. Thus, the characteristics of low contact
resistance and a low operating voltage, which cannot be realized by the
conventional electrostatic relay, can be realized.
If the voltage between the electrodes 4 and 20 is made to be zero, the
deformation caused from the torsional elasticity of the elastic torsional
portion 3 can be restored. Thus, the movable structure portion 10 is
restored to the non-operation state shown in FIG. 2.
According to the first embodiment, the following effects can be obtained.
The elastic connection portion 14 is disposed between the movable electrode
20 and the movable contact 22 of the movable structure portion 10
constituting the relay structure. When voltage is applied between the
fixed electrode 4 and the movable electrode 20, the deformation caused
from the torsional elasticity causes the fixed contact 5 and the movable
contact 22 to be brought into contact with other in the parallel state.
Therefore, the contacts 5 and 22 can be brought into plane contact with
each other so that sufficiently low contact resistance and a
satisfactorily large contact electric current capacity are obtained.
The distance between the electrodes 4 and 20 of the electrostatic actuator
can considerably be shortened as compared with the state of FIG. 3 which
is a limit of the conventional structure. Even if the electrostatic
attractive force is enlarged and the operating voltage is low,
sufficiently high pressure can be applied to the contacts. Therefore, an
electrostatic relay which can be operated with low operating voltage can
be realized.
Since the movable electrode 20 is covered with the insulating layer 21, a
problem of short circuit that the electrodes 4 and 20 are brought into
direct contact with each other can reliably be prevented. Although the
insulating layer 21 is interposed between the movable electrode 20 and the
fixed electrode 4, reduction in the electrostatic attractive force caused
from existence of the insulating layer 21 is not required to be considered
(ignored) because the insulating layer 21 is made of a dielectric material
having a high dielectric constant as compared with that of air.
Although the first embodiment has the structure that the elastic connection
portion 14 uses the torsional elasticity of the beam, the structure of the
elastic connection portion is not limited to this. The required structure
is such that the elastic connection portion is disposed to cause the
movable contact and the fixed contact to be brought into contact with each
other in a parallel state by dint of the elastic deformation when the
operating voltage is applied to the electrostatic relay. Thus, the elastic
modulus is required to enable deformation to take place with which the
electrostatic attractive force generated between the fixed electrode and
the movable electrode are brought into contact with each other in a
parallel state. For example, a cantilever beam shape extending from the
movable-electrode support portion 12 may be employed to obtain a similar
effect.
Second Embodiment
FIGS. 5 to 8 show a second embodiment of the present invention. Referring
to the drawings, a movable structure portion 30 constituting a relay
structure is held such that a gap is maintained from a substrate 1 through
an anchor structure 2 by an elastic torsional portion 3 in the form of the
beam shape. The movable structure portion 30 incorporates a
movable-electrode support portion 32, a movable contact support portion 33
and an elastic connection portion 34 for connecting the elastic torsional
portion 3 in the form of the beam shape and the movable-electrode support
portion 32 to each other with a predetermined length. The elastic
connection portion 34 formed into a plurality of sections which are
narrower than the movable-electrode support portion 32. Elastic
deformation (deformation caused from deflection) in a direction
perpendicular to the upper and lower surfaces causes the movable-electrode
support portion 32 and the movable contact support portion 33 to be
deformed and moved.
A movable electrode 20 and a movable. contact 22 are formed on the surface
of the movable structure portion 30 which is the relay structure opposite
to the substrate, as shown in FIGS. 6 to 8. A fixed electrode 4, an
insulating layer (a dielectric layer) 6 covering the surface of the fixed
electrode 4 and a fixed contact 5 are formed on the surface of the
substrate opposite to the foregoing elements. The fixed electrode 4
secured to the surface of the substrate 1 and the movable electrode 20
secured to the movable-electrode support portion 32 constitute an
electrostatic actuator which generates electrostatic attractive force when
voltage is applied between the fixed electrode 4 and the movable electrode
20.
The other structures are similar to those according to the first
embodiment.
The principle of the operation of the electrostatic relay according to the
second embodiment will now be described. FIG. 6 shows the positions of the
electrodes and contacts in a non-operation state (in a state in which no
voltage is applied). The space between the contacts 5 and 22 is opened.
When voltage is applied between the fixed electrode 4 and the movable
electrode 20 constituting the electrostatic actuator, electrostatic
attractive force is generated between the two electrodes. Thus, the
movable structure portion 30 which is the relay structure is, as shown in
FIG. 7, rotated toward the substrate until the movable contact 22 is
brought into contact with the fixed contact 5 by dint of the torsional
elasticity of the elastic torsional portion 3 in the form of the beam
shape.
In the conventional electrostatic relay, the operation of the relay
structure is interrupted at the foregoing time. Therefore, there arise
problems of insufficiently small contact area, unsatisfactorily low
contact pressure and high operating voltage as described above when the
operation of the first embodiment has been described.
However, the electrostatic relay according to this embodiment has the
structure that the elastic connection portion 34 having a predetermined
length is deflected and deformed by dint of the sucking force of the
electrostatic actuator. Thus, as shown in FIG. 8, the movable electrode 20
and the fixed electrode 4 are brought to a parallel state or a state near
the parallel state. Also the movable contact 22 and the fixed contact 5
are deformed so that they are brought to the parallel state. As can be
understood from FIG. 8, the contacts 5 and 22 are in plane contact with
each other in the parallel state at the foregoing time. Thus, sufficiently
low contact resistance and a large contact electric current capacity can
be obtained. Moreover, the distance between the electrodes 4 and 20 of the
electrostatic actuator can be shortened such that they are substantially
in contact with each other through the insulating layer 6 as compared with
the state shown in FIG. 7. Thus, considerably large electrostatic
attractive force can be generated. Therefore, a sufficiently high pressure
can be applied to the contacts even with low operating voltage. Thus, the
characteristics of low contact resistance and low operating voltage, which
cannot easily be realized by the conventional electrostatic relay, can
easily be realized.
As described above, according to the second embodiment, the elastic
connection portion 34 which can be deflected and deformed and which has a
predetermined length is disposed between a rotation fulcrum P (a center of
torsion of the elastic torsional portion 3 in the form of the beam shape)
of the movable structure portion 30 which is the relay structure and the
movable electrode 20. Thus, when voltage is applied between the fixed
electrode 4 and the movable electrode 20, the movable electrode 20 can be
sucked in parallel to the fixed electrode 4 or into a state near the
parallel state by dint of elastic deformation. Thus, the electrostatic
attractive force can be enlarged. Moreover, the contacts 5 and 22 are
brought into plane contact with each other so that sufficient low contact
resistance and a satisfactorily large contact electric current capacity
can be obtained. Thus, an electrostatic relay exhibiting low operating
voltage can be realized.
The second embodiment has elastic connection portion 34 formed such that
the elastic deformation of the elongated portion of the movable structure
portion 30 having a predetermined length in the perpendicular direction
with respect to the substrate is used. The structure of the elastic
connection portion is not limited to the foregoing structure. The elastic
connection portion is required to be disposed in such a manner that the
movable electrode and the fixed electrode are in parallel with each other
by dint of elastic deformation when operating voltage is applied to the
electrostatic relay. Thus, the elastic modulus is required with which the
electrostatic attractive force generated between the fixed electrode and
the movable electrode enables deformation to be performed in such a manner
that the two electrodes are in parallel with each other or in a state near
the parallel state. For example, torsional rotation of the beam of the
elastic connection portion 14, for example, as shown in FIG. 1 may be
employed to obtain a similar effect.
Third Embodiment
FIGS. 9 to 11 show a third embodiment of the present invention. The elastic
connection portion is formed between the movable electrode and a movable
contact in the movable structure portion which constitutes the relay
structure. Moreover, the elastic connection portion is also formed between
the fulcrum of rotation (a center of torsion of the torsional elasticity
portion in the form of the beam shape) of the movable structure portion
and the movable electrode. Referring to the drawings, a movable structure
portion 40 constituting a relay structure is held such that a gap is
maintained from an insulating substrate 1 through an anchor structure 2 by
an elastic torsional portion 3 in the form of the beam shape. The movable
structure portion 40 incorporates a beam support portion 41 having a
predetermined length and formed into the beam shape, a movable-electrode
support portion 42, a movable-contact support portion 43, a first elastic
connection portion 44 for connecting the leading end of the beam support
portion 41 and the movable-electrode support portion 42 to each other and
a second elastic connection portion 45 for connecting the
movable-electrode support portion 42 and the movable-contact support
portion 43 to each other. The first and second elastic connection portions
44 and 45 are torsional elasticity portions in the form of the beam shape.
The movable-electrode support portion 42 is supported rotatively with
respect to the leading end of the beam support portion 41 in the form of
the beam shape by the first elastic connection portion 44. The
movable-contact support portion 43 is rotatively supported with respect to
the leading end of the movable-electrode support portion 42 by the second
elastic connection portion 45.
The other structures are similar to those according to the foregoing first
embodiment and the same or similar portions are given the same reference
numerals and they are omitted from description.
FIGS. 10 and 11 show the operation of the electrostatic relay according to
the third embodiment. FIG. 10 shows the positions of electrodes and
contacts in a non-operation state (in a state in which no voltage is
applied). When voltage is applied between the fixed electrode 4 and the
movable electrode constituting the electrostatic actuator, electrostatic
attractive force is generated between the two electrodes. Thus, as shown
in FIG. 11, the movable structure portion 40 which is the relay structure
causes the movable contact 22 to be brought into contact with the fixed
contact 5 by dint of the torsional elasticity deformation of the elastic
torsional portion 3 in the form of the beam shape. Moreover, the torsional
elasticity deformation of the first and second elastic connection portions
44 and 45 causes rotation to be performed until the movable contact 22 and
the fixed contact 5 are brought into close contact with each other in a
parallel state.
As can be understood from FIG. 11, an appropriate elastic modulus of each
of the first and second elastic connection portions 44 and 45 which are
torsional elasticity portions is employed in the third embodiment. Thus,
the movable electrode 20 and the fixed electrode 4 can be brought to
opposite positions such that the movable electrode 20 and the fixed
electrode 4 of the electrostatic actuator are made to be substantially in
parallel with each other and an air gap is maintained. Thus, larger
electrostatic attractive force can be obtained as compared with the
structure in which the wedge shape air gap is provided as shown in FIG. 3.
Moreover, contact between the movable electrode 20 and the fixed electrode
4 can completely be prevented. Therefore, no insulating layer is required
on the movable electrode 20 or the fixed electrode 4 for constituting the
electrostatic actuator. As an alternative to this, the insulating pressure
resistance can be lowered. In addition, a problem in that the electrodes
of the actuator when the electrodes are undesirably brought into contact
with each other can be prevented.
Fourth Embodiment
FIGS. 12 and 13 show a fourth embodiment of the present invention. In this
embodiment, the relay structure is extended from the substrate to the two
sides of the torsional elasticity portion in the form of the beam shape
which rotatively supports the relay structure. Moreover, the relay
structure is disposed symmetrically with respect to the torsional
elasticity portion in the form of the beam shape. That is, the
electrostatic relay according to the fourth embodiment incorporates an
insulating substrate 1, an anchor structure 2 stood erect on the substrate
1 and secured to the same, an elastic torsional portion 3 held such that a
gap is maintained from the substrate 1 by the anchor structure 2 and
formed into the beam shape and movable structure portions 10A and 10B
rotatively disposed on the two sides by dint of the elastic support
performed by the elastic torsional portion 3 and constituting the relay
structure. Electrode and contacts of the movable structure portions 10A
and 10B are similar to those according to the first embodiment. Therefore,
the same or similar elements are given the same reference numerals and
they are omitted from description.
According to the fourth embodiment, inverse output voltage as shown in FIG.
14 is applied between the electrodes 4 and 20 of the right and left
electrostatic actuators when the electrostatic relay is operated. Thus,
when either of the relay contact 5 or 22 is turned off, the operation for
separating the contacts can be performed also by the electrostatic
attractive force of the opposite electrostatic actuator as well as the
restoring operation by dint of the elasticity of the elastic torsional
portion 3 in the form of the beam shape. Thus, the relay contact can
reliably be turned off.
If either of the electrode of the right and left fixed contacts is commonly
connected as shown in FIG. 12, the switch can easily be constituted as
shown in FIG. 15.
Another structure may be employed in which a pair of the movable contact 22
of either of the movable structure portion 10A or 10B and an opposite
fixed contact 5 adjacent to the substrate is omitted. Thus, the
reliability in the turning off operation can be improved.
In the above-mentioned embodiments, the movable electrode which is either
of the electrodes of the electrostatic actuator is formed on the surface
of the relay structure (the movable structure portion) adjacent to the
substrate. The position of the electrode is not limited to the foregoing
position. The substantial necessity lies in that the electrostatic
attractive force can be generated between the fixed electrode and the
movable electrode. If the structure of the electrostatic actuator, that
is, the relay structure is made of an insulating material having a high
dielectric constant or a material having high resistance, the movable
electrode may be disposed on the surface of the relay structure adjacent
to the substrate. If the foregoing structure is made of a conductive
material, the foregoing structure may be the movable electrode.
The movable contact 22 disposed at the end of the relay structure (the
movable structure portion) is not limited to one. A plurality of the
movable contacts 22 may be provided.
The present invention will furthermore specifically be described such that
examples will now be described.
FIGS. 16 and 17 are a plan view and a side view of the electrostatic relay
according to this example. In this example, a single crystal Si plate 51
having a SiO2 insulating layer 51a having a thickness of about 1 .mu.m and
formed by a thermal oxidation method as shown in FIG. 18A was used as the
substrate. Then, Au having a thickness of about 500 nm was formed on the
overall surface of the substrate by a sputtering method. Then, a
photoetching method was employed so that a fixed electrode 54 of the
electrostatic actuator and a fixed contact 55 of the relay were patterned.
Then, a reactive sputtering method was employed to form a SiN insulating
layer having a thickness of about 100 nm on the overall surface of the
substrate. Similarly, the photoetching method was employed to selectively
remove the foregoing insulating layer such that the surface of the fixed
electrode 54 of the electrostatic actuator was left. Thus, an insulating
layer 56 was formed.
Then, a vacuum CVD method was employed as shown in FIG. 18B so that a SiO2
film which was formed into a sacrifice layer 81 was deposited on the
overall surface of the substrate such that the thickness of the SiO2 film
was about 3 .mu.m. Subsequently, a RIE method is employed to selectively
etch a part of SiO2 film corresponding to the movable contact 72 by
approximately 500 nm. Then, an Au film having a thickness of about 500 nm
was formed on the overall surface of the substrate together with a SiN
reaction preventive layer having a thickness of about 20 nm. Then,
patterning into predetermined shapes was performed by photoetching so that
a movable electrode 70 of the electrostatic actuator and a movable contact
72 of the relay were formed. Then, a portion 82 of the sacrifice layer 81
corresponding to the anchor structure 52 in the form of the SiO2 film was
selectively removed by using photoetching.
Finally, the vacuum CVD method was employed to form a polycrystal Si film
83 on the overall surface of the substrate to have a thickness of about 4
.mu.m, as shown in FIG. 18C, and then patterned into the shape of the
relay structure to be described later by using a RIE method.
Then, the SiO2 film of the sacrifice layer 81 was selectively etched by HF
so that a movable structure portion 60 which is formed into the relay
structure as shown in FIGS. 16 and 17 was obtained by releasing.
The torsional elastic portion 53 in the form of the beam shape has a length
a from the anchor structure 52 which was about 100 .mu.m and a width of
about 6 .mu.m. The movable structure portion 60 constituting the relay
structure incorporates a beam connection portion 61 having a length b of
about 100 .mu.m and in the form of the beam shape, a movable-electrode
support portion 62 having a width c and a length d of about 200 .mu.m, a
torsional elasticity connection portion 64 having a width of about 6 .mu.m
and a length e of about 50 .mu.m and formed into the beam shape and a
movable-contact support portion 63 having a length f of about 50 .mu.m.
The overall body of the movable structure portion 60 can be rotated by
torsional elasticity of the torsional elastic portion 53 formed into the
beam shape. Moreover, the movable-contact support portion 63 can be
rotated by the torsional elasticity of the elastic connection portion 64
formed into the beam shape.
When operating voltage of about not higher than 20 V was applied between
the electrodes 54 and 70 constituting the electrostatic actuator of the
electrostatic relay according to the present invention, the contacts 55
and 72 are closed. At this time, the contact resistance was about 0.2
.OMEGA.. Thus, a 100 mA or higher contact electric current could be
passed. The foregoing value is a satisfactorily practical value for a
relay for a small signal. For example, the shape and dimensions are
changed such that the thickness of the SiO2 film which is formed into the
sacrifice layer can be reduced and the areas of the electrodes of the
electrostatic actuator can be enlarged. Thus, the operation can be
performed with lower voltage.
As a comparative example, a conventional structure was manufactured which
had a similar basic structure and which was not provided with the elastic
connection portion for elastically supporting the movable-contact support
portion. The comparative example was evaluated. As a result, although the
operating voltage was about not higher than 20 V, high contact resistance
of 5 .OMEGA. to 10 .OMEGA. was realized. To lower the contact resistance
to 1 .OMEGA. or lower, an operating voltage of 50 V or higher was
required. When a contact electric current of several mA was passed, the
contacts were melted and fixed. Thus, the operation for turning the
structure off was impossible.
As can be understood from the foregoing description, the electrostatic
relay according to the present invention is able to easily manufacture a
practical electrostatic relay exhibiting low voltage operation, low
contact resistance and a large contact capacity which have been impossible
for the conventional structure.
Although this example has the structure that the thin film forming
technique is employed to form the movable structure portion which is the
relay structure. The method of forming the electrostatic relay according
to the present invention is not limited to the foregoing structure. For
example, the movable structure portion may be formed such that the movable
contact and the movable electrode are formed on a single crystal Si
substrate. Moreover, an anisotropic etching technique or the like is
employed to realize a required shape so as to be bonded to an insulating
substrate similarly having a fixed contact and a fixed electrode through a
spacer. Also in the above-mentioned case, an electrostatic relay can
easily be obtained which exhibits low voltage operation and a large
contact capacity.
As the movable structure portion serving as the relay structure, a thin
metal plate having a surface subjected to an insulating process may be
employed. The electrostatic relay manufactured by the above-mentioned
method can be applied to a purpose in which a higher contact electric
current is passed as compared with the electrostatic relay manufactured by
the thin film forming technique.
Although the invention has been described in its preferred form, it is
understood that the present disclosure of the preferred form can be
changed in the details of construction and in the combination and
arrangement of parts without departing from the spirit and the scope of
the invention as hereinafter claimed.
As described above, the electrostatic relay according to the present
invention is able to overcome the problems experienced with the
conventional electrostatic relay in that insufficiently small contact
electric current capacity and rise in the contact resistance cannot be
overcome. According to the present invention, the contacts can be brought
into plane contact with each other. Thus, a large contact capacity and low
contact resistance can be realized.
Moreover, the problems-experienced with the conventional structure in that
the distance between the electrodes constituting the electrostatic
actuator cannot sufficiently be shortened when the operation is performed
and thus the contact pressure is insufficiently low, the contact
resistance rises and the operating voltage is raised to overcome the
foregoing problems can be overcome by the structure of the present
invention. Since the distance between the electrodes can considerably be
shortened as compared with the conventional structure, sufficiently high
contact pressure and low contact resistance can be realized with the
operating voltage lower than that required for the conventional structure.
As a result of the significant improvement in the relay characteristics,
the present invention is able to realize a practical electrostatic relay
as compared with the conventional electrostatic relay.
Fifth Embodiment
Embodiments of an electrostatic relay according to second aspect of the
present invention will now be described with reference to the drawings.
FIGS. 19 to 25 show a fifth embodiment of an electrostatic relay according
to the present invention. FIG. 19 is a plan view. FIGS. 20 to 25 are front
cross sectional views showing the operation. Referring to the drawings,
the electrostatic relay incorporates an insulating substrate 1, an anchor
structure 2 stood erect on the substrate 1 and secured to the same, an
elastic torsional portion 3 held such that a gap is maintained from the
substrate 1 and formed into a beam shape and a relay structure 7 which is
able to rotate (revolve) by dint of elastic support by the elastic
torsional portion 3. As a result of the above-mentioned structure, the
relay structure 7 is rotatively held such that the elastic torsional
portion 3 serves as rotation fulcrum P. Since the relay structure 7
intersects the elastic torsional portion 3 so as to be formed into a
seesaw structure extending to the two sides of the rotation fulcrum P, the
relay structure 7 is able to perform a seesaw motion.
The insulating substrate 1 has a structure that at least the surface
thereof is subjected to an insulating process. For example, the substrate
1 is a single crystal Si substrate having a SiO2 insulating layer formed
on the surface thereof. The three elements, which are the anchor structure
2, the elastic torsional portion 3 in the form of the beam shape and the
relay structure 7, are integrally formed by polycrystal Si or the like.
The relay structure 7 has a movable structure portion (a main body of the
relay structure) 10 arranged to perform a seesaw operation and having
required rigidity. In the left-hand portion of the relay structure 7, an
elastic torsional portion 11L in the form of the beam shape serving as an
elastic connection portion is formed. Moreover, a movable-electrode
support portion 12L (a movable electrode portion for which a movable
electrode is provided) connected to a movable structure portion 10 through
the elastic torsional portion 11L is formed. In a right-hand portion which
is symmetrical with respect to the rotation fulcrum P of the movable
structure portion 10, an elastic torsional portion 11R in the form of the
beam shape and a movable-electrode support portion 12R (a movable
electrode portion for which a movable electrode is provided) are formed.
The elastic torsional portions 11L and 11R in the form of the beam shape
rotatively (in a revolving permitted manner) support the movable-electrode
support portions 12L and 12R. The elastic torsional portions 11L and 11R
in the form of the beam shape are formed adjacent to the rotation fulcrum
P of the movable structure portion 10, while the movable ends of the
movable-electrode support portions 12L and 12R are formed apart from the
rotation fulcrum P of the movable structure portion 10. The positions of
elastic torsional portions 11L and 11R in the form of the beam shape are
rotation fulcrums L and R of the movable-electrode support portions 12L
and 12R. The torsional elastic modulus of each of the elastic torsional
portions 11L and 11R in the form of the beam shape is made to be smaller
than that of the elastic torsional portion 3 in the form of the beam
shape. That is, the movable-electrode support portions 12L and 12R can be
rotated with relatively small force as compared with the movable structure
portion 10.
Movable electrodes 13L and 13R are provided for the movable-electrode
support portions 12L and 12R at positions opposite to the substrate 1.
Fixed electrodes 4L and 4R are formed on the substrate 1 at positions
opposite to the corresponding movable electrodes. As shown in FIG. 20,
insulating layers (dielectric layers) 5L and 5R covering the surfaces of
the fixed electrodes are formed.
Movable-contact support portions 14L and 14R are integrally formed at two
ends of the movable structure portion 10 which is the main body of the
relay structure 7. Movable contacts 15L and 15R are provided for the
surfaces of the movable-contact support portions 14L and 14R opposite to
the substrate. Fixed contacts 6L and 6R are fixed to the surface of the
substrate 1 at positions opposite to the corresponding movable contacts.
The fixed electrodes 4L and 4R secured to the surface of the insulating
substrate 1 and the movable electrodes 13L and 13R secured to the
movable-electrode support portions 12L and 12R constitute an electrostatic
actuator for generating electrostatic attractive force by dint of voltage
applied between the movable electrodes 13L and 13R secured to the
movable-electrode support portions 12L and 12R. The fixed electrodes 4L
and 4R and the movable electrodes 13L and 13R are connected to an outer
power source through electric wires (not shown).
The principle of the operation of the electrostatic relay according to the
fifth embodiment will now be described. Initially, the operation for
closing the relay contact will now be described.
FIG. 20 shows the positions of the electrodes and the contacts in a
non-operation state (in a state where no voltage is applied). In the
foregoing state, the fixed contacts 6L and 6R and the movable contacts 15L
and 15R are opened. When voltage is applied between the fixed electrode 4R
and the movable electrode 13R constituting the right-hand electrostatic
actuator, electrostatic attractive force is generated between the two
electrodes. Thus, the movable-electrode support portion 12R is rotated
around the rotation fulcrum R by dint of the torsional elasticity of the
elastic torsional portion 11R in the form of the beam shape. As a result,
the movable-electrode support portion 12R is deformed to a contact
position of the substrate 1 as shown in FIG. 21 (the movable electrode 13R
is deformed until it is brought into contact with the insulating layer 5R
covering the fixed electrode 4R). The electrostatic attractive force
acting between the fixed electrode and the movable electrode of the
electrostatic actuator is in proportion to the inverse square of the
distance. Therefore, as can be understood also from FIG. 21, considerably
great electrostatic attractive force is generated between the fixed
electrode 4R and the movable electrode 13R disposed such that their
distance has been shortened to have a wedge shape air gap. As shown in
FIG. 22, the movable structure portion 10 which is the main body of the
relay structure 7 is rotated to the right such that the rotation fulcrum P
serves as the center of rotation. Thus, the movable contact 15R and the
fixed contact 6R are brought into contact with each other so that the
relay contact is closed.
In a state in which the relay contact has been closed, the wedges shape air
gap between the movable electrode 13R and the fixed electrode 4R is
narrowed, as shown in FIG. 22. Thus, a high contact pressure can be
obtained.
As described above, the electrostatic relay according to the fifth
embodiment of the present invention has the structure that the
movable-electrode support portion 12R which is rotated with small force is
operated in an initial stage of application of the voltage to the
electrostatic actuator in which the electrodes of the electrostatic
actuator are distant from each other and the electrostatic attractive
force is small. Thus, the distance between the electrodes is shortened.
The shortened distance between the electrodes causes considerable large
force to be generated between the electrodes of the electrostatic
actuator. The large force rotates the main body of the relay structure 7,
that is, the movable structure portion 10 which is the outer frame portion
of the movable-electrode support portion around the rotation fulcrum P.
Thus, the relay contact is closed and a higher pressure can be applied
between the contacts.
Therefore, when the electrostatic relay is used at the same operating
voltage as that of the conventional electrostatic relay, the contact
resistance can be lowered. Since larger force can be obtained when the
contacts are closed, the elastic modulus of the elastic torsional portion
3 in the form of the beam shape for supporting the relay structure 7 can
furthermore be enlarged. Therefore, if fixing of the contacts takes place,
the contacts can easily be separated from each other.
That is, when the same voltage is used to operate the electrostatic relay
according to this embodiment as that of the conventional electrostatic
relay, breakdowns of a type fixing of the contacts can be prevented. Thus,
a higher contact electric current can be passed. If the contact capacity
is the same as that of the conventional electrostatic relay, the operation
can be permitted with lower operating voltage.
The operation for opening the relay contact will now be described.
FIG. 23 shows a state in which the electrodes of the right-hand
electrostatic actuator are short-circuited (the same potential) and the
electrostatic attractive force on the right-hand side has been made to be
zero after the relay contact shown in FIG. 22 has been actuated. In the
above-mentioned state, the force for separating the contacts 6R and 15R
from each other is only the restoring force caused from the elastic
modulus of the elastic torsional portion 3 in the form of the beam shape
which elastically supports the movable structure portion 10 which is the
main body of the relay structure 7.
If the force for fixing the contacts 6R and 15R is larger than the
foregoing restoring force, the contacts of the electrostatic relay are not
opened. Thus, a failure of a type that the contacts are fixed takes place.
The conventional electrostatic relay may be formed such that voltage is
applied between the electrode of the left-hand electrostatic actuator so
as to cause the relay structure to perform the seesaw operation so that
the force for separating the right-hand contact is generated.
However, as can be understood from FIG. 23, the movable structure portion
10 of the movable electrode 13L of the left-hand electrostatic actuator is
inclined. Thus, the movable electrode 13L is greatly distant from the
fixed electrode 4L as compared with the non-operation state shown in FIG.
20. Therefore, satisfactorily large electrostatic attractive force cannot
be generated. As a result, sufficiently large force for separating the
right-hand contacts 6R and 15R cannot be generated.
In the fifth embodiment of the present invention, when voltage is applied
between the movable electrode 13L and the fixed electrode 4L of the
left-hand electrostatic actuator in the state shown in FIG. 23, the
movable-electrode support portion 12L which can be rotated with small
force is rotated such that the rotation fulcrum L serves as the center of
rotation, as shown in FIG. 24. Thus, the movable-electrode support portion
12L is deformed to the position of contact with the substrate 1 (deformed
until the movable electrode 13L is brought into contact with the
insulating layer 5L covering the fixed electrode 4L)
The electrostatic attractive force acing between the fixed electrode and
the movable electrode of the electrostatic actuator is inverse proportion
to the square of the distance. Therefore, a considerably great
electrostatic attractive force is generated between the movable electrode
13L and the fixed electrode 4L, the distance between which has been
shortened in the form of the wedge shape air gap. Thus, great attractive
force is generated for narrowing the wedge shape air gap.
The great electrostatic attractive force rotates the movable structure
portion 10 which is the main body of the relay structure 7 to the left
with large force. Thus, the right-hand movable contact 15R and the fixed
contact 6R which have been fixed to each other can be separated from each
other with large force, as shown in FIG. 25.
According to the fifth embodiment, the following effects can be obtained.
The movable-electrode support portions 12L and 12R provided for the movable
structure portion 10 at the positions on the two sides of the rotation
fulcrum P are rotatively connected to the movable structure portion 10 by
dint of the elastic torsional portions 11L and 11R serving as the elastic
connection portions and formed in the beam shape. When voltage is applied
between either of the right-hand or left-hand fixed electrode and the
movable electrode to operate the right-hand or left-hand electrostatic
actuator, the movable-electrode support portion approaches the substrate
so that the distance between the fixed electrode and the movable electrode
is shortened. Therefore, even low voltage is sufficient to turn the relay
contact on with a sufficiently high contact pressure.
When the relay contact is turned off, application of voltage to the
electrostatic actuator opposite to a melted contact enables great
separating force to be generated as compared with the conventional
electrostatic relay even if the contacts encounter the phenomenon of
melting. Thus, the failure of the type that the contacts are melted can be
prevented.
Since the fixed electrodes 4L and 4R are covered with the insulating layers
5L and 5R, a problem of short circuit such that the fixed electrodes 4L
and 4R are brought into directly contact with the movable electrodes 13L
and 13R can reliably be prevented. Although the insulating layers 5L and
5R are interposed between the fixed electrodes 4L and 4R and the movable
electrodes 13L and 13R, the insulating layers 5L and 5R are made of the
dielectric materials having a larger dielectric constant as compared with
that of air. Therefore, reduction in the electrostatic attractive force by
dint of existence of the insulating layers 5L and 5R is not required to be
considered (can be ignored).
As a result, a practical electrostatic relay can be realize which exhibits
a low-voltage operation, low contact resistance and a large contact
capacity.
Sixth Embodiment
FIGS. 26 to 32 show a sixth embodiment of the electrostatic relay according
to the present invention. FIG. 26 is a plan view. FIGS. 27 to 32 are front
cross sectional views showing the operation. Referring to the drawings, a
relay structure 7A has, on the left-hand portion thereof, elastic
torsional portion 21L serving as an elastic connection portion and formed
into the beam shape and a movable-electrode support portion 22L connected
to a movable structure portion 10A (the main body of the relay structure
7A) through the elastic torsional portion 21L. Moreover, an elastic
torsional portion 21R in the form of the beam shape and a
movable-electrode support portion 22R are formed on the right-hand portion
symmetrical with respect to the rotation fulcrum P of the movable
structure portion 10A which is the main body of the relay structure 7A.
The elastic torsional portions 21L and 21R in the form of the beam shape
rotatively support the movable-electrode support portions 22L and 22R.
However, this embodiment is different from the fifth embodiment in that
the elastic torsional portions 21L and 21R in the form of the beam shape
are formed adjacent to the two ends of the movable structure portion 10A.
The movable ends of the movable-electrode support portions 22L and 22R are
positioned adjacent to the rotation fulcrum P. The positions of the
elastic torsional portions 21L and 21R in the form of the relay are the
rotation fulcrums L and R of the movable-electrode support portions 22L
and 22R. The elastic modulus of each of the elastic torsional portions 21L
and 21R in the form of the beam shape is made to be not larger than that
of the elastic torsional portion 3 in the form of the beam shape. That is,
the movable-electrode support portions 22L and 22R can be rotated with the
force which is not larger than that required for rotating the movable
structure portion 10A.
Movable electrodes 23L and 23R are provided for the movable-electrode
support portions 22L and 22R at positions opposite to the substrate 1.
Fixed electrodes 4L and 4R are secured to the surface of the substrate 1
at positions opposite to the movable electrodes. Insulating layers
(dielectric layers) 5L and 5R covering the surfaces of the fixed
electrodes are formed. Movable contacts 15L and 15R are provided for the
surfaces of the movable-contact support portions 14L and 14R at the two
ends of the movable structure portion 10A opposite to the substrate. Fixed
contacts 6L and 6R are secured to the surface of the substrate 1 at
positions opposite to the corresponding movable contacts. Since the other
portions are similar to those according to the fifth embodiment, the same
and corresponding portions are given the same reference numerals and they
are omitted from description.
The principle of the operation of the electrostatic relay according to the
sixth embodiment will now be described. Initially, the operation for
closing the relay contact will now be described.
FIG. 27 shows the positions of the electrodes and contacts in a
non-operation state (in a state in which no voltage is applied). The fixed
contacts 6L and 6R and the movable contacts 15L and 15R are opened. When
voltage is applied between the fixed electrode 4R and the movable
electrode 23R constituting the right-hand electrostatic actuator,
electrostatic attractive force is generated between the two electrodes.
Thus, the movable-electrode support portion 22R is rotated by dint of the
torsional elasticity of the elastic torsional portion 21R in the form of
the beam shape such that the rotation fulcrum R serves as the center.
Thus, the movable-electrode support portion 22R is deformed to the
position of contact with the substrate 1 (deformed until the movable
electrode 23R is brought into contact with the insulating layer 5R
covering the fixed electrode 4R), as shown in FIG. 28. The electrostatic
attractive force acting between the fixed electrode and the movable
electrode of the electrostatic actuator is inverse proportion to the
square of the distance. Therefore, as can be understood from also FIG. 28,
considerably large electrostatic attractive force is generated between the
fixed electrode 4R and the movable electrode 23R, the distance between
which has been shortened such that a wedge shape air gap is maintained.
Thus, large attractive force for narrowing the wedge shape air gap is
generated. As shown in FIG. 29, the movable structure portion 10A which is
the main body of the relay structure 7A is rotated to the right such that
the rotation fulcrum P serves as the center of rotation. As a result, the
movable contact 15R and the fixed contact 6R are brought into contact with
each other. Thus, the relay contact is closed.
In a state where the relay contact has been closed, the wedge shape air gap
between the movable electrode 23R and the fixed electrode 4R is narrowed.
Therefore, a high contact pressure can be obtained.
As described above, the electrostatic relay according to the sixth
embodiment of the present invention has the structure that the
movable-electrode support portion 22R which is rotated with small force is
initially operated in an initial stage of application of voltage to the
electrostatic actuator in which the distance between the electrodes of the
electrostatic actuator is long and the electrostatic attractive force is
small. Thus, the distance between the electrodes is shortened. The
shortened distance between the electrodes causes considerably large force
to be generated between the electrodes of the electrostatic actuator. The
generated force rotates the main body of the relay structure 7A, that is,
the movable structure portion 10A which is an outer frame portion of the
movable-electrode support portion such that the rotation fulcrum P serves
as the center of rotation. Thus, the relay contact is closed and higher
pressure can be applied between the contacts.
The electrostatic relay according to the sixth embodiment of the present
invention and the electrostatic relay according to the fifth embodiment of
the same will now be compared with each other. The electrostatic relay
according to the sixth embodiment has the structure that the
movable-electrode support portion 22R has the rotation fulcrum R which is
the end of the relay structure 7A. Shift of the state shown in FIG. 21 to
the state shown in FIG. 22 according to the fifth embodiment and shift of
the state shown in FIG. 28 to that shown in FIG. 29 are compared with each
other. Since the force for rotating the movable structure portion 10A of
the main body of the relay structure 7A is applied to the rotation fulcrum
R of the movable-electrode support portion 22R distant from the rotation
fulcrum P of the movable structure portion 10A, larger rotational force
can be used to rotate the movable structure portion 10A by dint of the
principle of a lever.
Therefore, as compared with the electrostatic relay according to the fifth
embodiment, when the electrostatic relay is operated with the same
operating voltage, the elastic modulus of the elastic torsional portion 3
for supporting the movable structure portion 10A which is the main body of
the relay structure 7A can furthermore be enlarged. Therefore, fixed
contacts can easily be separated from each other if fixing of the contacts
takes place.
That is, as compared with the conventional electrostatic relay, when the
operation is performed with the same voltage, the failure of the type that
the contacts are fixed can furthermore be prevented as compared with the
electrostatic relay according to the fifth embodiment. Thus, a higher
contact electric current can be passed. If the contact capacity is the
same as that of the conventional electrostatic relay, the operation can be
performed with lower operating voltage.
As can be understood from a comparison between FIGS. 22 and 29, the wedge
shape air gap formed between the movable electrode and the fixed electrode
in the state in which the relay contact has been closed is smaller in the
sixth embodiment as compared with the fifth embodiment. Thus, larger
electrostatic attractive force can be generated, the contact pressure
between the fixed contact and the movable contact can be raised and the
contact resistance can be lowered.
Therefore, in the sixth embodiment, the contact resistance caused when the
contacts have been closed can furthermore be lowered. Therefore, if the
same contact electric current is passed, the generation of Joule heat in
the contact portion can be prevented. Thus, generation of the melting of
the contacts owning to rise in the temperature of the contact portion can
furthermore be prevented.
A structure may be employed in which the torsional elasticity of each of
the elastic torsional portions 21L and 21R in the form of the beam shape
for rotatively connecting the movable-electrode support portions 22L and
22R to the movable structure portion 10A and the torsional elasticity of
the elastic torsional portion 3 in the form of the beam shape are made to
similar to each other. Thus, the force required to rotate the
movable-electrode support portions 22L and 22R and that required to rotate
the movable structure portion 10A to be similar to each other. In the
foregoing case, the processes shown in FIGS. 28 and 29 take place
simultaneously. Also in the foregoing case, the forces for bringing the
relay contacts (fixed contacts 6L and 6R and the movable contacts 15L and
15R) into contact with each other are finally made to be similar to each
other.
The operation for opening the contacts will now be described.
FIG. 30 shows a state in which the electrodes of the right-hand
electrostatic actuator are short-circuited (the same potential) after the
relay contact shown in FIG. 29 has been turned on and thus the right-hand
electrostatic attractive force has been made to be zero. In the foregoing
state, the force for separating the contacts 6R and 15R from each other is
only the restoring force generated by the elastic modulus of the elastic
torsional portion 3 in the form of the beam shape for elastically
supporting the movable structure portion 10A which is the main body of the
relay structure 7A.
If the force for fixing the contacts 6R and 15R to each other is larger
than the foregoing restoring force, the contacts of the electrostatic
relay are not opened. Thus, a failure of the type that the contacts are
fixed takes place.
Also the sixth embodiment has the structure that voltage is applied between
the electrodes of the left-hand electrostatic actuator so as to cause the
movable structure portion 10A which is the main body of the relay
structure 7A to perform the seesaw motion. Thus, the force for separating
the right-hand contact is generated.
The operation at the foregoing time is shown in FIGS. 30 and 31. As can be
understood from FIG. 30, the electrostatic relay according to this
embodiment has the structure that the movable end 22La of the left-hand
movable-electrode support portion 22L of the electrostatic relay is
positioned adjacent to the rotation fulcrum P of the movable structure
portion 10A. Therefore, although the movable structure portion 10A is
inclined to the right, distance d' from the movable end 22La to the fixed
electrode 4L opposite to the movable end 22La is substantially the same as
distance d realized in a stationary state shown in FIG. 27.
The force for rotating the movable-electrode support portion 22L is the
force of a lever with respect to the rotation fulcrum L. The distance d'
from the movable end 22La to the fixed electrode is substantially the same
as that in the stationary state shown in FIG. 27 (that is, also the
distance from the end of the movable electrode 23L adjacent to the movable
end 22La which generates maximum rotational force to the fixed electrode
is substantially the same as that realized in the stationary state shown
in FIG. 27). Therefore, application of voltage between the electrodes
causes the movable-electrode support portion 22L to easily be rotated.
Thus, shift to the state shown in FIG. 31 can be performed. When the
movable end 22La of the movable-electrode support portion 22L and the end
of the movable electrode 23L are formed adjacently to each other as much
as possible, the restoring force can efficiently be generated.
Therefore, if the elastic modulus of each of the elastic torsional portions
21L and 21R in the form of the beam shape for rotatively supporting the
movable-electrode support portions 22L and 22R is not made to be a small
value as is set in the fifth embodiment shown in FIGS. 23 and 24,
application of usual operating voltage enables the movable-electrode
support portion 22L to reliably be rotated. Thus, the distance from the
movable electrode 23L to the fixed electrode 4L can be shortened.
As shown in FIG. 31, considerably large electrostatic attractive force is
generated between the movable electrode 23L and the fixed electrode 4L,
the distance between which has been shortened in the form of the wedge
shape air gap. Thus, large force for narrowing the wedge shape air gap can
be generated.
As described above, with the electrostatic relay according to the sixth
embodiment, even if the right-hand relay contact is fixed, application of
usual operating voltage between the left-hand electrodes causes the
movable-electrode support portion 22L to reliably be rotated. Thus, the
operation is performed in the initial stage of the application of the
voltage to the electrostatic actuator in which the distance between the
electrodes of the electrostatic actuator is short and the electrostatic
attractive force is small so that the distance between the electrodes is
shortened. As a result of the shortened distance between the electrodes,
considerably large force is generated between the electrodes of the
electrostatic actuator. The generated force rotates the movable structure
portion 10A so that the right-hand relay contacts, that is, the fixed
contact 6R and the movable contact 15R are opened, as shown in FIG. 32.
In the electrostatic relay according to this embodiment, the
movable-electrode support portion 22L is rotated such that the end of the
movable structure portion 10A which is the main body of the relay
structure 7A of the movable-electrode support portion 22L serves as the
fulcrum of rotation. Therefore, when the state shown in FIG. 31 to the
state shown in FIG. 32, as compared with the shift according to the fifth
embodiment to the state shown in FIG. 25, the force for rotating the
movable structure portion 10A acts on the fulcrum L of the
movable-electrode support portion 22L distant from the rotation fulcrum P
of the movable structure portion 10A. Therefore, the principle of a lever
enables the movable structure portion 10A to be rotated with larger force.
Therefore, employment of the structure according to this embodiment
enables larger force for separating the fixed contacts to be generated as
compared with the fifth embodiment.
If the contacts encounter the phenomenon of melting, the electrostatic
relay according to the sixth embodiment of the present invention is able
to generate separating force which is larger than the separating force
which can be generated in the fifth embodiment as compared with the
conventional electrostatic relay when voltage is applied to the
electrostatic actuator opposite to the melted contacts. Thus, the failure
of melting of the contacts can furthermore reliably be prevented. The
other operations and effects are similar to those obtainable from the
foregoing fifth embodiment.
The foregoing fifth and sixth embodiments have the structure that one pair
of the movable-electrode support portion and a movable electrode is
provided with respect to the relay structure. The present invention is not
limited to this. For example, plural pairs of the movable electrode
portions (that is, the movable-electrode support portions and movable
electrodes) may be provided to be adaptable to the shape of the relay
structure. If the same function can be realized, a thru structure except
for the symmetrical structure may be employed to meet a purpose.
Although the foregoing fifth and sixth embodiments have the structure that
the movable electrodes are formed on the surface of the substrate of the
relay structure, the positions of the electrodes are not limited to the
foregoing positions. The necessity substantially lies in that the
electrostatic attractive force can be generated between the fixed
electrode and the movable electrode. If the relay structure is made of an
insulating material having a high dielectric constant or a high-resistance
material, the movable electrode may be disposed on the opposite surface of
the substrate of the relay structure. If the relay structure is made of a
conductive material, the relay structure may be formed into the movable
electrode (in the foregoing case, the movable-electrode support portion is
not required and the movable electrode portion forms the movable
electrode).
As the positions of the relay contacts composed of the pairs of the fixed
contacts and the movable contacts, the foregoing embodiments have been
described about the structure which is able to form a relay circuit having
the relay contacts at the two ends of the relay structure to perform the
complementary operation. If a single contact is permitted, the relay
contact may be provided for only one side. A plurality of contacts may be
provided for the relay structure so as to permit simultaneously
opening/closing of a plurality of circuits.
In the above-mentioned fifth and sixth embodiments, torsional elastic
portions in the form of the beam shape are employed as the elastic
connection portions for connecting the movable structure portion and the
movable electrode portion which form the main body of the relay structure.
If a similar function can be realized, a structure except for the
torsional elastic portion may be employed.
The present invention will furthermore specifically be described such that
examples will now be described.
FIGS. 33 and 34 are a plan view and a front cross sectional view showing an
electrostatic relay according to this example. The foregoing electrostatic
relay has a structure similar to that according to the sixth embodiment.
In this example, a single crystal Si plate 1 having a SiO2 insulating
layer 1a having a thickness of about 1 .mu.m and formed by a thermal
oxidation method as shown in FIG. 35A was used as the substrate. Then, Au
having a thickness of about 500 nm was formed on the overall surface of
the substrate by a sputtering method. Then, a photoetching method was
employed so that the fixed electrodes 4L and 4R of the electrostatic
actuator and the fixed contacts 6L and 6R of the relay were patterned.
Then, a reactive sputtering method was employed to form a SiN insulating
layer having a thickness of about 100 nm on the overall surface of the
substrate. Similarly, the photoetching method was employed to selectively
remove the foregoing insulating layer such that the fixed electrodes 4L
and 4R of the electrostatic actuator were left. Thus, insulating layers 5L
and 5R were formed.
Then, a vacuum CVD method was employed as shown in FIG. 35B so that a SiO2
film which was formed into a sacrifice layer 31 was deposited on the
overall surface of the substrate such that the thickness of the SiO2 film
was about 3 .mu.m. Subsequently, an RIE method is employed to selectively
etch portions of SiO2 film corresponding to the movable contacts 15L and
15R by approximately 500 nm. Then, an Au film having a thickness of about
500 nm was formed on the overall surface of the substrate together with a
SiN reaction preventive layer having a thickness of about 20 nm. Then,
patterning into predetermined shapes was performed by photoetching so that
the movable electrodes 23L and 23R of the electrostatic actuator and the
movable contacts 15L and 15R of the relay were formed. Then, a portion 32
of the sacrifice layer 31 corresponding to the anchor structure 2 in the
form of the SiO2 film was selectively removed by using photoetching.
Finally, the vacuum CVD method was employed to form a polycrystal Si film
33 on the overall surface of the substrate to have a thickness of about 4
.mu.m, as shown in FIG. 35C, and then patterned into the shape of the
relay structure 7A to be described later by using a RIE method. Then, the
SiO2 film of the sacrifice layer 31 was selectively etched by HF so that
the relay structure 7A as shown in FIGS. 33 and 34 was obtained by
releasing.
As shown in FIG. 33, the relay structure 7A incorporates elastic torsional
portions 3a and 3b having length a which was about 140 .mu.m from the
anchor structure 2 and a width of about 6 .mu.m and formed into the beam
shape; the movable structure portion (the frame portion) 10A extending to
the right and left from the elastic torsional portions 3a and 3b in the
form of the beam shape such that each of the portions had a length b of
about 220 mm and serving as the main body of the relay structure 7A; the
torsional elastic portions 21La, 21Lb, 21Ra and 21Rb formed at positions
extending, for about 200 .mu.m, to the right and left from the elastic
torsional portions 3a and 3b in the form of the beam shape, each having a
length c of about 80 .mu.m and a width of about 3 .mu.m and formed into
the beam shape; the movable-electrode support portions 22L and 22R
connected to the foregoing elastic portions and having a length d of about
150 .mu.m and a width e of about 200 .mu.m; and the movable-contact
support portions 14L and 14R having a length of about 50 .mu.m. The
overall body of the relay structure 7A including the foregoing elements is
rotatable by the torsional elasticity of each of the elastic torsional
portions 3a and 3b in the form of the beam shape. Moreover, the
movable-electrode support portions 22L and 22R can be rotated by the
torsional elasticity of each of the torsional elastic portions 21La, 21Lb,
21Ra and 21Rb in the form of the beam shape.
When operating voltage of about not higher than 20 V was applied between
right or left electrostatic actuators of the electrostatic relay according
to the present invention, the relay contacts were closed. At this time,
the contact resistance was about 0.2 .OMEGA.. When 100 mA contact electric
current was passed, the contacts were free from melting. When 200 mA
contact electric current was passed, the contacts were melted. However,
application of the operating voltage to the electrostatic actuator
opposite to the melted relay contact enabled the contacts to easily be
restored.
As described above, the electrostatic relay according to this embodiment
enables satisfactorily practical characteristics as a relay for small
signals to be obtained. For example, the shape and dimensions are changed
such that the thickness of the SiO2 film which is formed into the
sacrifice layer 31 in the manufacturing process shown in FIGS. 35A to 35C
can be reduced and the areas of the electrodes of the electrostatic
actuator can be enlarged. Thus, the operation can be performed with lower
voltage.
As a comparative example, a conventional structure was manufactured which
had a similar basic structure and dimensions and which was not provided
with the rotatable movable-electrode support portion and in which the
movable electrodes were secured to the main body of the relay structure so
as to be evaluated. As a result, although the operating voltage was about
not higher than 20 V, high contact resistance of 5 .OMEGA. to 10 .OMEGA.
was realized. To lower the contact resistance to 1 .OMEGA. or lower, an
operating voltage of 40 V or higher is required. When a contact electric
current of several mA was passed, the contacts were melted. Thus, the
operation for turning the structure off was impossible. Even if an
operating voltage of 20 V was applied to the electrostatic actuator
opposite to the melted contacts, the contacts could not be opened.
As described above, employment of the electrostatic relay according to the
present invention enables a practical electrostatic relay to be formed
which exhibits low-voltage operation, low contact resistance, a high
contact capacity and satisfactory reliability.
Although the foregoing embodiments have been described about the structure
in which the relay structure is formed by using the thin film forming
technique, the method of forming the electrostatic relay according to the
present invention is not limited to the foregoing method. For example, a
method may be employed in which a movable contact and a movable electrode
are formed on a single-crystal Si substrate to obtain the relay structure.
Then, an anisotropic etching technique or the like is employed to realize
a required shape so as to be bonded to an insulating substrate similarly
having a fixed contact and a fixed electrode through a spacer.
Also in the above-mentioned case, an electrostatic relay can be obtained
with which a large contact capacity and low-voltage operation can easily
be realized as compared with the conventional structure and which exhibits
satisfactory reliability.
As the relay structure, a thin metal plate having a surface subjected to an
insulating process may be employed. The electrostatic relay manufactured
by the above-mentioned method can be applied to a purpose in which a
higher contact electric current is passed as compared with the
electrostatic relay manufactured by the thin film forming technique.
Although the invention has been described in its preferred form, it is
understood that the present disclosure of the preferred form can be
changed in the details of construction and in the combination and
arrangement of parts without departing from the spirit and the scope of
the invention as hereinafter claimed.
As described above, according to the present invention, the problems
experienced with the conventional electrostatic relay in that the contact
electrodes are easily melted and fixed, a sufficiently high contact
electric current cannot be maintained and reliability and practicality are
unsatisfactory can be overcome. Thus, an electrostatic relay can be
realized which exhibits low contact resistance, a large contact electric
current capacity and low operating voltage, with which failures of a type
that the contacts are melted and fixed and which has satisfactory
reliability.
Since the characteristics as the relay can significantly be improved, the
electrostatic relay according to the present invention enables a relay
exhibiting satisfactory practicality as compared with the conventional
electrostatic relay to be constituted.
Top